Abrading element and method of making same



Patented Mar. 1949 ABRADING ELEMENT AND METHOD E MAKING SAME Jefferson Paul Buckey, Easton, Conn.; John F. McGowan, administrator of said J eiferson'laulv Buckey, deceased, asslgnor to John T. Kilbrlde,

Stratl'ord, Conn.

No Drawing. Application January 16, 1945,- Serial No. 573,132

The present invention relates to abrasive elements and particularly to those having therein isotropic vitrescent carbon derived from carbohydrates and the methods of making such elements. I

Heretofore when grinding tungsten carbide or other hard alloys or metals, it was necessary to rely upon diamond wheels or carborundum wheels to make the cut. These wheels are very expensive and efforts to produce less expensive wheels have been unsuccessful. l

In attempting to make .these less expensive wheels, efforts were made to incorporate carbon in grinding elements in the form of activated graphite and as carbon derived from hydrocarbons, but these were not satisfactory due to .the unctuous nature of the material which acted as a lubricant and also caused the wheel to load or cause particles of metal to be transferred thereto.

These proposed wheels, and even some of the Carborundum wheels, when used to cut tungsten carbide or the like would not make a clean cut but would Produce a burned or dragged surface. All of these wheels had to be dressed frequently and had a relatively short operative life.

These disadvantages have been overcome by the present invention by incorporating in the grinding element or wheel small amounts of ismtropic vitrescent carbon derived from carbohydrates. The carbon is in a very pure crystalline state and is uniformly distributed throughout the grinding element. Small percentages in the grinding element will greatly increase its cutting properties.

While the present invention may be applled to various types of grinding elements, it is preferably employed in revolving abrasive bodies such as wheels or elements thereof or reciprocating abrasive bodies since the heat and pressure generated by the moving abrasive body causes the isotropic vitrescent carbon, in conjunction with the grain and bond of such abrasive bodies, to momentarily reach a hardness not approximated anywhere on the Moh scale of hardness. but sufficient to cut and sharpen sintered carbide with a speed and brilliance equal to that of a diamond.

The carbon bearing elements of the present in- A vention are particularly well suited for grinding, cutting, shaping, sharpening or polishing ferrous or non-ferrous metals, sintered carbides and other powder-metal compositions or bodies as well as fused non-metallic bodies such as brick, tile, stones, crystalsand-other natural or manufactured bodies.

11 Claims. (Cl. 51-295) The carbon may be included in both resin wheels and in vitrified wheels and may be incorporated in the wheels in several different ways. In the case of a resin bond or other similarly bonded wheels, it may be directly incorporated in the mixture'of the wheel as in finely ground particles of the carbon. Where it is desired to incorporate the carbon in a vitrified or resin bonded wheel and at the same time harden the wheel, it may be put into the wheel by the hot process of soaking the wheel in a sugarsolution and then gradually bring up the temperature of the wheel to reduce the sugar and dry out the wheel. However, if it is desired not to materially alter the hardness of these wheels, the carbon is placed in a colloidal suspension and the wheels soaked therein and dried.

The carbon presently preferred is produced from refined cane sugar since itis readily available and free of impurities such as iron, sulphur and the like which affect the grinding properties. However, it is to be understood that the carbon may be made from other sugars, molasses, starch or the like carbohydrates when the presence of impurities is not objectionable. Throughout the specification and claims the term "sugar carbon" is used todenote a carbon produced from any one of these substances.

In preparing the carbon for direct incorporation into a wheel, a quantity of sugar is placed in an oven and the temperature in the oven gradually increased up to 500 F. The sugar is left in the oven until it has become completely reduced to pure carbon. As this occurs, it becomes a hard .porous mass of fine isotropic vitrescent carbon crystals. The mass is then ground in a mill to about 325 mesh Tyler and is then ready for incorporation with the mix of the wheel. The resultant carbon crystals are then mixed with the usual constituents for grindin wheels having phenolic resins or other thermoplastic or thermosetting binders, shellac, resinoid, or other bonds, and the wheel is then subjected to the usual drying heat necessary to set the binder and harden the wheel. This heat is not sufiiciently high to destroy the carbon. It has been found that resinoid wheels employing cutting grain composed of fused aluminum oxide, silicon carbide, emery, garnet or quartz having only a small percentage of isotropic vitrescent carbon therein will readily However, wheels may have from .025% to 10% by weight of isotropic vitrescent carbon therein as dictated by the nature of the work which they are required to do.

It is to be pointed out that isotropic vitrescent carbon may be used in wheels other than resin wheels, for example, a very satisfactory cutting wheel has been made by combining 50 parts by weight of Portland cement, 50 parts by weight of quartz, and parts by weight of isotropic vitrescent carbon. The mixture is formed into a wheel, dried and hardened in the usual manner. This wheel cuts extremely hard materials with greater facility than does a wheel made up without the isotropic vitrescent carbon. v

The temperature required to produce vitrescent wheels is so high that if the carbon crystals are mixed with the composition of the wheel before it is baked, they would be destroyed in the baking process. Accordingly, the present invention provides for distributing the isotropic vitrescent carbon in the wheel after it has been baked. One method of accomplishing this isto dissolve refined cane sugar in water to produce a solution having a preferred Baum reading of between 2 and 4. The yfinished vitrescent wheel is placed in a tank of the sugar solution and-permitted to remain there until the pores of the wheel have been thoroughly filled with the solution.

If desired, the wheels may be subjected to a vacuum to draw out the air in the pores and increase the speed with which the solution penetrates the wheel.

After the wheel has been thoroughly saturated with the sugar solution, it is briefly drained and then placed in an oven and the temperature gradually raised to 500 F., the rate of temperature increase being dependent upon the size and structure of the wheel; large thick wheels of great density requiring a slow temperature rise to avoid thermal shock due tounequal expansion of the outer and inner parts of the wheels whereas smaller wheels can be increased rapidly since their size and density permits substantially equal expansion throughout their grain and bond structure.

As the water is driven off by the heat, the sugar in the wheel is reduced and the carbon crystals form and begin to expand in the pores with the result that every pore "of the wheel is filled with hard vitreous isotropic crystal carbon. The amount of carbon which is to be found in the wheel can be controlled by controlling the Baum reading of the sugar solution which may vary between a Baum of .0083 to a Baum of 27.1.

Furthermore, if greater polishing action is desired in the wheel, a small percentage of finely divided chemically pure alumina may be added into the wheel by the a wheel and the wheel vitrified. After being vitrified and dressed, the wheel weighed 60 pounds. The wheel was then treated as outlined above to include the carbon therein and after the treatment it weighed 60.2 pounds. This wheel was used for grinding extremely hard bolts. It produced a better ground surface and had an operative life of seven times that of an untreate wheel.

In cases where it is not desired to increase the hardness of the wheel but to maintain it substantially at its normal hardness, I have discovered that the carbon may be put into the wheel by a.cold method by forming a colloidal suspension of vitrified isotropic carbon derived from carbohydrates and soaking the finished vitrified wheel in this colloidal suspension of carbon until the pores of the wheel are completely filled thereby. The wheel thus saturated is briefly drained and placed in an oven and the temperature gradually increased until the wheel has been thoroughly dried. Since this carbon has already expanded during its formation, it does not expand during. the dryingperiod and hence the internal tension of the wheel is not increased and the wheel retains approximately its original hardness. Here again, the amount of carbon inserted in the wheel may be readily controlled by controlling the colloidal suspension into which the wheel is placed and the amount of carbon placed in the suspension will be determined by the use to which the wheel is to be put.

Not only may these last methods be used to incorporate the carbon in vitrified wheels but they may also be used to cause the carbon to be incorporated in any type of porous wheel whether it be resin bonded or of other types.

With all of the processes the temperature is preferably limited to 500 F. to avoid afiecting the bonds in the wheels. However, when this is not a factor the temperature may be taken up to approximately 950 F. before the carbon crystals are destroyed.

It has been discovered that the abrading materials in the wheels of the present invention, in addition to performing their usual function of cutting as in other wheels, serve to support and backup the carbon particles. During the process of abrading and cutting metals or other substances, the carbon particles are momentarily placed under great pressure and heat, considering the size of the particle, with the'result that the particle becomes a cutting and abrading agent unequalled by any substance excepting the diamond.

By any of the methods of the present invention the isotropic vitrescent carbon will uniformly and completely incorporate into the wheel in such a manner that the wheel maker may read ily and accurately control the carbon content and hardness of the finished wheels. The carbon willbe so thoroughly distributed that it will be contiguous to almost every cutting part of the wheel.

Wheels made in accordance with the present invention and having therein the istropic vitrescent carbon derived from carbohydrates have the advantage that they not only cut extremely hard materials but produce a high finish thereon in contrast to the dark lusterless finish heretofore produced in the cutting operation. It is believed that this is due to the heated carbon crystals combining with the oxygen which would otherwise go to the'heated metal to oxidize the same.

Not only will the wheel of the present invention cut hard materials such as used in cutting tools but it .will also cut the softer metal which carries the cutting material with equal facility and without tearing the metal away as has been the case with diamond and other similar wheels used for this purpose.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

Iclaim:

1. An abrasive element comprising a body of abrasive material, said body containing crystalline sugar carbon. a

2. An abrasive element comprising a body of abrasive material, said body having isotropic vitrescent sugar carbon crystals therein.

3. An abrasive element comprising a body containing uniformly distributed isotrOpic vitrescent sugar carbon crystals throughout.

4. An abrasive element having .7 by weight of isotropic vitrescent sugar carbon crystals uniformly distributed throughout.

5. An abrasive element having between .025% to by weight of isotropic vitrescent sugar carbon crystals uniformly distributed throughout.

6. An abrasive element comprising abrasive grits, crystalline sugar carbon, and a resinous bonding material.

'I. A vitrified abrasive element comprising a. body of abrasive material, said body including crystalline sugar carbon.

8. A grinding element comprising abrasive grits, a bonding material, and crystalline sugar carbon.

6 27.1, immersing a porous grinding element in the sugar solution and saturating the wheel, and heating the wheel up to substantially 500 F, to drive on the water and reduce the sugar solution in the wheel to vitrescent isotropic carbon crystals.

11. The method'of producing .a grindingwheel comprising the steps of preparing a su ar solution having a Baum reading or between-2 to 4, immersing a porous grinding wheel in the sugar solutionand saturating the wheel, and heating the wheel to a temperature below substantially 500 F. to drive off the water and reduce the sugar solution in the wheel to vitrescent isotropic 9. The method of producing a movable grinding element comprising the steps of preparing a sugar solution, immersing a porous grinding element in the sugar solution and saturating the element, and heating the element to drive off the water and reduce the sugar to vitrescent isotropic carbon crystals, the crystals expanding and becoming bound in the element.

10. The method of producing a. grinding wheel comprising the steps of preparing a sugar solution having a Baum reading between .0083 and 'carbon crystals.

JEFFERSON PAUL BUCKEY.

REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 19,802 Pohl et al Dec. 31, 1935 53,032 Nelson Mar. 6, 1866 1,099,984 Kirsten June 16, 1914 1,573,061 Hartmann Feb. 16, 1926 1,625,463 Gauthier Apr. 19, 1927 2,125,782 Heald Aug. 2, 1938 FOREIGN PA'IENTS Number Country Date 448,454 Great Britain June 8, 1936 OTHER REFERENCES Bibliography of Solid Absorbents, by Victor B. Deitz, published by U. S. Cane Sugar Refiners and Bone Char Mfg. and Bureau of Standards. 

